1. Field of the Invention
The present invention generally relates to an electronic timepiece provided with a calendar function. More specifically, the present invention relates to an electronic timepiece provided with a calendar function, for example, an electronic timepiece with calendar function capable of automatic end of the month correction, and a control method for the same.
2. Background Information
Electronic timepieces with a calendar mechanism to display a calendar (electronic timepiece with calendar function) are well known. The calendar display mechanism of the timepiece provides a mechanism to rotate a calendar display wheel such as a day panel (day display wheel), for example, on which are arranged numerals 1 through 31 on the circular periphery thereof, the rotation being accomplished through a gear system in conjunction with the rotation of a rotor. Further, an actuator controls the amount of rotation of the rotor to rotate the day wheel one day.
Electronic timepieces provided with such a calendar display mechanism are further provided with an end of the month correction function to avoid a remainder display at the end of those months which have fewer than 31 days (February, April, June, September, November) because days are only incremented one day at a time, and the nonexistent remaining days are actually displayed. For an example, please refer to WIPO Publication WO99/34264 and Japanese Laid-Open Patent Publication No. 2003-25563, which are hereby incorporated by reference. Specifically, when the calendar display mechanism is a mechanism which displays year, month, and day, a day detecting part and month detecting part are respectively provided to detect the displayed month and day in conjunction with the amount of rotation of the day panel and month panel or the like; after the day is advanced, the currently displayed year, month, and day are detected by the day detecting part and month detecting part. Then, if the detected day is a nonexistent day, the actuator is controlled to rotate the day panel or the like until an existing day is displayed. Consequently, an accurate calendar date is displayed in the date window.
When the amount of rotation of the rotor is controlled by an actuator, the drive of the actuator and the detection of the amount of rotation of the rotor are accomplished in parallel. Conventionally, however, since a photoreflector (reflecting type photosensor) is used in the detection of the rotation of the rotor, there is concern that the rated current of the drive power source may be exceeded when the actuator and photoreflector are driven simultaneously (that is, when the calendar is advanced). This problem is particularly pronounced when a secondary battery is used in the drive power source.
In a timepiece provided with an end of the month correction function, the calendar displayed by the calendar display mechanism (calendar displayed in the display window of the timepiece) must be detected, and whether the detected date includes an existing day must be determined. A problem arises in this calendar detection inasmuch as considerable power is consumed when a plurality of photoreflectors is used. When many mechanical switches are used, however, a problem arises inasmuch as the service life of the mechanical switch is reduced, a large torque acts upon the gear train of the calendar display mechanism, and the power consumption of the actuator increases.
Conventionally, all calendar information displayed by the calendar display mechanism must be detected for end of the month correction. Therefore, there is an increase in the power consumed for calendar detection when the calendar displays a plurality of calendar information such as month, day and the like. When sensors, such as photoreflectors (reflecting type photosensors), are used, which have relatively large power consumption, the rated current of the drive power source may be exceeded when a plurality of detection parts are simultaneously operated. This problem is particularly pronounced when a secondary battery is used in the drive power source.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved electronic device with a calendar function and control method for the same. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.